The aim of this project is to estimate the volatilization of mercury from various components of terrestrial and aquatic landscapes in the Carson River Basin. The aim will be achieved through a combination of controlled laboratory studies and field surveys designed to establish the range of volatilization rates and the role of physical, chemical and biological factors in controlling the rates of volatilization. The more specific objective is to empirically describe via a multiple regression model volatilization as a function of a host of biotic and abiotic factors so that estimates of volatilization can be offered for any combination of site and time (e.g., time of year) by knowing a few select parameters that in large measure control volatilization. The statistical modeling effort will be interfaced with the diversity of disciplinary expertise in this proposal (fields of biology, ecology, atmospheric chemistry, hydrology and photochemistry) to interpret the mechanisms underlying the statistical association between mercury volatilization rate and a given environmental factor or factors. A smaller set of measurements will also be made to determine the concentration of mercury in the atmosphere, which attention to both gaseous and particle components. This will assist in efforts designed to understand the potential exposure pathways to biota, including humans. The rationale for these studies is twofold. The first is simply to understand the spatial and temporal variation in the pathways and fate of mercury in the environment, particularly in a region in which contamination is elevated due to anthropogenic factors. The second is to characterize the landscape-to-atmosphere flux of mercury in undisturbed areas of the Carson River Basin, which is a representative site of the mercuriferous belts of the Earth. It is hypothesized that sites in these belts are the predominant natural sources of mercury in the atmosphere.